Bloody hell.
All that I can think of to say is the usual protests in defense of NASA, which I have enormous respect for--space flight is extraordinarily dangerous by it's very nature, and the fact that in 42 years we've had what--three?--fatal incidents is staggering. NASA's safety record is astonishingly good. What I remember about the Challenger was how badly it set back the space program, and I pray to whatever forces watch over manned space flight that it doesn't happen again. If people in Congress use this as yet another excuse to gut NASA's budget...well, it'd be a bloody poor sort of memorial.
The only thing that keeps me from total despair on that front is that other countries, like China, are actively working to develop a space program, and while the U.S. government won't lift a finger these days to fund space flight for it's own sake, the money will flow like wine to make damn sure that we're the top dog. I don't know much about the space programs in other countries, but I wish them all the luck and speed possible.
For the loss of human life today, it'll take better people than I to say anything useful about it. There's never enough brave people in the world, and losing so many in such a fashion hurts us all.